The present invention relates to fuel properties estimating apparatus and process for an internal combustion engine.
A vehicle known as flexible fuel vehicle (FFV) can run on a blend fuel of alcohol and gasoline as well as on gasoline. Alcohol fuel requires a large amount of fuel injection as compared to gasoline to obtain a given equivalence ratio because of the different number of atoms of C (carbon). Therefore, an engine system as shown in a Published Japanese Patent Application Publication No. H05(1993)-163992 (pages 1˜4, and FIG. 5) is arranged to sense an alcohol concentration with an alcohol concentration sensor provided in a fuel tank or to estimate the alcohol concentration from an average value of air-fuel ratio feedback correction coefficient in the case of a failure of the alcohol concentration sensor.